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Old 10-02-10, 03:08 PM   #1
Noobtastic
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Is my chain line so bad?

I just finished putting together my first single speed and it is riding ok except for 2 bent spokes on the front wheel and the chain line issue that I want to address. Here are pictures from the front and rear if they help:




I've ridden it around the neighborhood and ridden it up a few steep hills but the chain stays right on. It's when I start to speed or crank up a hill at speed that it derails inwards. So far I have not redished the wheel because I managed to prevent it from touching the chainstay by flipping the axle assembly then moving the axle slightly to the right.
I thought I'd go to the bike shop to get the wheel redished till I noticed that I'm using the original 3/32" 40t chainring and a shimano freewheel that was sold to me as a 3/32" cog that is compatible with both 3/32" and 1/8" chains. I can move the chain side to side on both the chainring and cog very easily and I'm wondering if this is the reason why the chain keeps derailing. Would a 3/32" chain solve this problem?
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Old 10-02-10, 07:35 PM   #2
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Easy to fix, go to the lbs and ask them for a BB cup spacer, or a BB spacer, many mtb shimano crankset kits have them just in case and lbs usually do not use them so thye should have a few moving around. If they charge you 20 bucks for a couple send them to hell and never come back to that shop, new ones only u can find them pretty cheap, so the guys should be able to give you a few for free. The spacers are like 2 mm thick

Take the freewheel off and put the spacer between the hub and the freewheel. That will bring the freewheel off and the chain line will be better. In that way u dont need to do a single thing like redish the wheel and stuff.

Good luck.
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Old 10-03-10, 08:18 AM   #3
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Thanks, I'm going to get a wheel truing lesson at a local community bike shop and I bet the owner has some spacers. I'll also switch the chains just to make sure that isn't the issue either; I figured I can buy one new 3/32" chain for my mountain bike and put it's worn out chain on this new bike and hopefully that will stay on. I really want to commute on this by wednesday
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Old 10-03-10, 08:36 AM   #4
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The spacer is the fastest and cheapest way.
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Old 10-03-10, 08:55 AM   #5
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The spacer is the fastest and cheapest way.
Though far from the best way.

You'll end up with fewer threads engaging the freewheel and still won't fix the dish. I'd suggest going to that wheel truing lesson with some axle spacers, get the chainline and spacing right and redish the wheel for more strength and longevity.
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Old 10-03-10, 01:01 PM   #6
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I don't think that a BB spacer is what you need in this case. Your first picture clearly shows that the chainring is out farther from the centerline than the freewheel cogs. And from the looks of things near as I can tell you'already have the ring mounted to the inside of the spider so that's as good as that is going to get without a BB swap to a shorter BB axle. And usually the freewheel on a SS sits a lot closer to the dropout than your pictures show. I think what happened is that you over did it when you just flipped the axle and spacers around. That was just too big a change.

So what you actually need is to fiddle around with the axle spacers to move the hub a little closer to the drive side dropout to achieve the optimum chainline. You probably caused this when you flipped the axle and spacers around, which was a rather crude and overkill method of gaining a bit of movement. Instead what you need is to get some different spacers and fine fit washers to alter the hub position so that the freewheel cogs are in plane with the chainring. A straight edge of some sort laided up to the side of the chain ring and extending back to the freewheel is a great tool for doing this. It quickly lets you see how far out the freewheel is from being in plane with the ring to easily a half millimeter or so.

Once you fiddle and select the axle spacers to align the hub and freewheel optimally on the drive side then select spacers and fine tuning washers for the other side so that your locknut to locknut span is the correct wheel spacing to match your dropout spacing. Then you can then worry about tuning your spokes to adjust the wheel dish to re-center the rim and tire between the chain stays.
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Old 10-03-10, 01:13 PM   #7
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Noob,
That chain line looks ok. As long as it not making a considerable amount of noise. My single speed has a chain line like that and it doesn't make any noise. If its not rubbing, it will not wear and you should have a bulletproof system.
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Old 10-03-10, 01:16 PM   #8
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Why did my head suddenly move to the right when i looked at that picture, lol. I think the chain line is OK, wear and noise will tell you otherwise.
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Old 10-03-10, 01:26 PM   #9
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I don't think that a BB spacer is what you need in this case.
If you read it again, ultraman was suggesting using a BB spacer (apparently free at his local bike shop, $3/ea at mine) behind the freewheel to space it out further. While that's usually fine for 1-2mm, my calibrated eyeball is telling me it's 1cm or better and requires a wheel redish as you suggested.

Better than guessing or even using a straightedge, you can measure the chainline and compare it with the rear.
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Old 10-03-10, 07:39 PM   #10
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I don't think it's really that big of a deal. You could still ride it around, but over time it's going to wear out the chain and cogs way faster. I wouldn't stop riding because of the slightly out of cant chain line, but I would get some spacers to rectify the problem so that you do have a straighter chainline.
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Old 10-03-10, 08:50 PM   #11
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I'd suggest going to that wheel truing lesson with some axle spacers, get the chainline and spacing right and redish the wheel for more strength and longevity.
+1. if you've already booked the lesson, just go ahead and bring the wheel. although, i'd go ahead and put the right amount of spacers in beforehand.
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Old 10-03-10, 10:16 PM   #12
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If you read it again, ultraman was suggesting using a BB spacer behind the freewheel to space it out further. While that's usually fine for 1-2mm, my calibrated eyeball is telling me it's 1cm or better and requires a wheel redish as you suggested......

Ah, I see. Sorry, my bad. I wasn't thinking of behind the freewheel.
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Old 10-04-10, 04:06 PM   #13
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If they charge you 20 bucks for a couple send them to hell and never come back to that shop
I laughed out loud.
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